The present invention relates to an electron beam lithography system, and especially, to an apparatus preferable for exposing LSI (Large Scale Integrated Circuit) patterns.
Methods for exposing LSI patterns and phase shift patterns on a target mask plate by a phase shift method exist in the art. Patterns exposed by the phase shift method are, for example, a part of the wiring layers, VIA holes, and contact holes which are especially wanted to be more precisely exposed than other patterns in whole LSI layers, and the phase shift patterns are respectively arranged around the above described partial patterns. Accordingly, in order to make the following explanation clear, such a square or a rectangular pattern as the contact hole is taken as an example pattern which is exposed by the phase shift method, and is called a main pattern or an original pattern in contrast with the phase shift pattern. The following explanation can be naturally applicable to other patterns.
The LSI pattern data are put into the electron beam lithography system after being converted in format by the data converter, and are exposed on the mask plate. During the above described process, the original pattern is exposed at a designated position.
Next, phase shift pattern data which is converted in format by the data converter is transferred to the electron beam lithography system, and the phase shift patterns are exposed around the original pattern.
In the phase shift method, the original pattern is exposed precisely by interference of light passing through the phase shift patterns with light passing through the original pattern when a chip region of a LSI wafer is exposed using the mask plate.
Accordingly, in order to cause the above described interference of light certainly at a designated portion, the position and the shape of the respective phase shift patterns are precisely and definitely defined depending on shape of the corresponding original pattern.
But, in such a conventional technique as above described, there was a problem in that a long time was needed because the pattern design, format conversion by the data converter, and exposure by the electron beam lithography system were independently repeated to both the original pattern and the phase shift pattern. For example, in a case of 0.3 .mu.m rule devices, about ten hours were required only for a format conversion of the phase shift pattern, and consequently, throughput was remarkably lowered.